How to reinforce a stained glass window is something that anyone who works with stained glass should learn. To avoid bowing and sagging over the years, windows that exceed 4 square feet in overall dimension should be as stable as possible. When a window is less than 4 square feet, the need to stabilize it will depend on the design and where the window will be installed.
The constant opening and closing of a door will cause a window to arch if it is not properly stabilized. Therefore, any window, no matter the size, that goes into a door, including cabinets, must be reinforced. The same is true of a window that is installed as an exterior window and is exposed to outside elements, especially the wind, or near a door that is frequently opened and closed.
To determine the square footage of a pattern or window, multiply the width by the height, in inches, then divide by 144. To convert the metric system to square feet, multiply the width by the height in centimeters, then divide by 930.25 .
When I say “depends on the design”, I mean straight lines that make hinge joints. A hinge joint is a straight or fairly straight line that allows the window to bend in half. You will often find those straight lines in geometric designs, but they can appear in any design. If the lines don’t go all the way across the window, they may go far enough to not only bend, but also break any glass that gets in their way. Folding can occur any time the window is not resting on the work surface. It’s no fun seeing the newly finished window bent in half, pulling the glass out of the lead or aluminum foil and perhaps smashing a bit of glass in the process.
So what can you use to reinforce stained glass? It’s called copper top dressing and it works with both copper foil and lead. Several manufacturers make copper plates. Cascade Metals and Venture are the two that I know. I’ve always used Cascade Metal batter, just because it’s what’s available where I buy my supplies. I have been using it for 20% 2B years.
Restrip will bend and follow curves easily as you use it, but it will not bend at the edge. In other words, hold a piece in your hands with the edge up and try to bend it by moving both hands inward (almost the same motion you use when breaking glass with your hand). It will not move. If you hold it with the flat surface up, you can easily fold it.
When using facing for reinforcement, it is important to remember that it must go from one edge of the window to the other. That’s the only way it will do any good. It can be horizontal or vertical, or both if necessary. When going both ways, one of the batter pieces will need to be cut where it intersects the other. It will then restart on the other side of the intersection. In other words, the 2 pieces
they will form a cross (% 2B) where they meet. Once the panel is soldered, the horizontal and vertical pieces will be joined from the solder that goes through the lead joint or the copper foil seam. There is nothing special you have to do to make that happen. It is a natural fact that happens when you weld.
Restrip can be used on both copper sheet and lead work. Using aluminum foil, the strip sits on the edge between the laminated glass pieces. The glass will need to be cut a little smaller to accommodate the thickness of the batter. Restrip is as thick as copper foil with the backing in place. If you are using a lead or zinc edge, follow the instructions below for lead.
With lead, the grid sits on the edge, in the lead channel. Make sure it goes from one outside edge to the other outside edge of the panel, with maybe 1/8 inch sticking out of each edge. Bend the protruding part up or down so that it lies flat against the outer edge of the glass. That will help the grid adhere to the inside of the edge wire once it is soldered. The principles are the same for grinding use regardless of whether you work with copper or lead foil.
Most stained glass suppliers can purchase a copper varnish to strengthen the stained glass.